BK, you haven't mentioned in your operatic encounters Benjamin Britten, and I've been thinking that, after listening to Krasa's Brundibar, you might like Britten's opera for children and adults, Noye's Fludde. This work really moves me to tears by its imagination, heart, and beauty; by the time the audience joins in singing the Navy Hymn (Eternal Father, strong to save) to calm the animals on the ark during the storm, I'm a complete mess.
Britten's live recording has some echo, but the three adults (Noah, Mrs Noah, and the Voice of God) and the six boys and girls playing Noah's sons and daughters-in-law are, as Goldilocks would say, just right.